Phase Stability of Nanocrystalline Grains of Rare-Earth Oxides (Sm2O3 and Eu2O3) Confined in Magnesia (MgO) Matrix

Chen Barad, Giora Kimmel, Hagay Hayun, Dror Shamir, Kachal Hirshberg, Yaniv Gelbstein

Research output: Contribution to journalArticlepeer-review

6 Scopus citations

Abstract

Rare-earth (RE) oxides are important in myriad fields, including metallurgy, catalysis, and ceramics. However, the phase diagram of RE oxides in the nanoscale might differ from the phase diagrams for bulk, thus attracting attention nowadays. We suggest that grain size in the nanoscale also determines the obtained crystallographic phase along with temperature and pressure. For this purpose, nanoparticles of Sm2O3 and Eu2O3 were mixed in an inert MgO matrix via the sol-gel method. This preparation method allowed better isolation of the oxide particles, thus hindering the grain growth process associated with increasing the temperature. The mixed oxides were compared to pure oxides, which were heat-treated using two methods: gradual heating versus direct heating to the phase transition temperature. The cubic phase in pure oxides was preserved to a higher extent in the gradual heating treatment compared to the direct heating treatment. Additionally, in MgO, even a higher extent of the cubic phase was preserved at higher temperatures compared to the pure oxide, which transformed into the monoclinic phase at the same temperature in accordance with the phase diagram for bulk. This indicates that the cubic phase is the equilibrium phase for nanosized particles and is determined also by size.

Original languageEnglish
Article number2201
JournalMaterials
Volume13
Issue number9
DOIs
StatePublished - 1 May 2020

Keywords

  • Oxide materials
  • Phase transformations
  • Scanning electron microscopy (SEM)
  • Sol-gel
  • X-ray diffraction

ASJC Scopus subject areas

  • Materials Science (all)

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